U.S. patent number 9,755,767 [Application Number 14/530,662] was granted by the patent office on 2017-09-05 for mechanism to measure, report, and allocate a highest possible rank for each cell in a carrier aggregation (ca) mode receiver-limited user equipment (ue).
This patent grant is currently assigned to QUALCOMM Incorporated. The grantee listed for this patent is QUALCOMM Incorporated. Invention is credited to Abhinav Dayal, Manjinder Singh Sandhu, Madhusudan Kinthada Venkata.
United States Patent |
9,755,767 |
Dayal , et al. |
September 5, 2017 |
Mechanism to measure, report, and allocate a highest possible rank
for each cell in a carrier aggregation (CA) mode receiver-limited
user equipment (UE)
Abstract
Certain aspects of the claimed invention generally relate to a
network dynamically configuring one or more cells based on signal
quality measurements received from all antennas of a
receiver-limited UE. The receiver-limited UE may have a number of
receivers that is less than or equal to a number of antennas of the
UE. Further, the UE may be capable of operating in a CA mode.
Dynamically configuring the one or more cells based, at least in
part, on the received signal quality measurements may allow the UE
to operate on M.times.N MIMO on the Pcell or Scell.
Inventors: |
Dayal; Abhinav (San Diego,
CA), Sandhu; Manjinder Singh (Poway, CA), Venkata;
Madhusudan Kinthada (San Diego, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
|
|
Assignee: |
QUALCOMM Incorporated (San
Diego, CA)
|
Family
ID: |
54337386 |
Appl.
No.: |
14/530,662 |
Filed: |
October 31, 2014 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20160127055 A1 |
May 5, 2016 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L
5/0028 (20130101); H04B 17/309 (20150115); H04B
7/0486 (20130101); H04L 5/0023 (20130101); H04W
24/10 (20130101); H04L 5/006 (20130101); H04W
16/24 (20130101); H04L 5/0091 (20130101); H04L
5/0085 (20130101); H04B 7/0413 (20130101); H04B
7/063 (20130101); H04L 5/001 (20130101); H04L
5/0048 (20130101); H04L 5/14 (20130101) |
Current International
Class: |
H04B
17/309 (20150101); H04W 16/24 (20090101); H04B
7/04 (20170101); H04B 7/06 (20060101); H04B
7/0413 (20170101); H04W 24/10 (20090101); H04L
5/00 (20060101); H04L 5/14 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
LTE-Advanced Physical Layer--IMT-Advanced Evaluation Workshop Dec.
17-18, 2009. cited by examiner .
Partial International Search
Report--PCT/US2015/053471--ISA/EPO--Dec. 23, 2015. cited by
applicant .
Ericsson et al., "Physical Layer Parameters to be Configured by
RRC", 3GPP Draft; R2-110857 L1 Parameters, 3rd Generation
Partnership Project (3GPP), Mobile Competence Centre, 650, Route
Des Lucioles, F-06921 Sophia-Antipolis Cedex, France, vol. RAN WG2,
No. Taipei, Taiwan, Feb. 21, 2011, Feb. 15, 2011 (Feb. 15, 2011), 4
pages, XP050493634, [retrieved on Feb. 15, 2011] the whole
document. cited by applicant .
International Search Report and Written
Opinion--PCT/US2015/053471--ISA/EPO--Apr. 5, 2016. cited by
applicant.
|
Primary Examiner: Rutkowski; Jeffrey M
Assistant Examiner: Ma; Basil
Attorney, Agent or Firm: Patterson & Sheridan, L.L.P
Claims
What is claimed is:
1. A method for wireless communication, comprising: receiving
signal quality measurements from all antennas of a receiver-limited
user equipment (UE) capable of operating in a carrier aggregation
(CA) mode, wherein a number of receivers of the UE is less than or
equal to a number of antennas of the UE; and dynamically
configuring at least one of a primary cell (Pcell) or a secondary
cell (Scell) of the UE, based at least in part, on the received
signal quality measurements, wherein the UE is a Category 5 or
higher UE and reports a maximum 2.times.2 multiple-input
multiple-output (MIMO) support for each CA band combination.
2. The method of claim 1, wherein receiving the signal quality
measurements comprises: receiving a first rank report from the UE
for the Pcell when the Scell is configured, wherein the first rank
report includes a reported rank of the Pcell, and wherein the
dynamically configuring comprises deactivating the Scell and
configuring the UE for MIMO operation on the Pcell, when the
reported rank of the Pcell equals the number of antennas at the
UE.
3. The method of claim 2, further comprising: configuring the UE
for a lower-order MIMO operation and activating the Scell when a
subsequently reported rank for the Pcell drops to a lower value as
compared to the reported rank of the Pcell in the first rank
report.
4. The method of claim 1, wherein dynamically configuring
comprises: scheduling at least one of activation or deactivation of
the Scell at a transmission time interval (TTI) level.
5. The method of claim 1, wherein receiving the signal quality
measurements comprises: receiving a first rank report from the UE
for the Pcell when the Scell is configured, wherein the first rank
report includes a reported rank of the Pcell, and receiving a
second rank report from the UE for the Scell, wherein the second
rank report includes a reported rank of the Scell, wherein the
dynamically configuring comprises deactivating CA and handing over
the UE to the Scell for MIMO operation on the Scell, when the
reported rank for the Scell equals the number of antennas at the
UE.
6. The method of claim 5, further comprising: configuring the UE
for a lower-order MIMO operation and activating CA when a
subsequently reported rank of the Scell drops to a lower value as
compared to the reported rank of the Scell in the second rank
report.
7. A method for determining a rank for a primary cell (Pcell) and a
secondary cell (Scell) in a wireless communication network, the
method comprising: sampling, in a first time interval, a reference
signal in the Pcell using a first antenna set and sampling a
reference signal in the Scell using a second antenna set; repeating
the sampling step in a second time interval; combining the sampled
reference signals from the first and second time intervals to
determine a rank for the Pcell and the Scell, respectively; and
reporting the determined rank of the Pcell and the Scell to the
network.
8. The method of claim 7, wherein the method is performed by a user
equipment (UE) in a carrier aggregation (CA) mode.
9. The method of claim 7, wherein the method is performed by a user
equipment (UE) that does not have measurement gaps scheduled by the
network.
10. The method of claim 7, wherein repeating the sampling step in
the second time interval comprises: sampling the reference signal
in the Pcell using the second antenna set and sampling the
reference signal in the Scell using the first antenna set.
11. An apparatus for wireless communication, comprising: means for
receiving signal quality measurements from all antennas of a
receiver-limited user equipment (UE) capable of operating in a
carrier aggregation (CA) mode, wherein a number of receivers of the
UE is less than or equal to a number of antennas of the UE; and
means for dynamically configuring at least one of a primary cell
(Pcell) or a secondary cell (Scell) of the UE, based at least in
part, on the received signal quality measurements wherein the UE is
a Category 5 or higher UE and reports a maximum 2.times.2
multiple-input multiple-output (MIMO) support for each CA band
combination.
12. The apparatus of claim 11, wherein the means for receiving the
signal quality measurements comprises means for receiving a first
rank report from the UE for the Pcell when the Scell is configured,
wherein the first rank report includes a reported rank of the
Pcell, and wherein the means for dynamically configuring comprises
means for deactivating the Scell and means for configuring the UE
for MIMO operation on the Pcell, when the reported rank of the
Pcell equals the number of antennas at the UE.
13. The apparatus of claim 12, further comprising: means for
configuring the UE for a lower-order MIMO operation and means for
activating the Scell when a subsequently reported rank for the
Pcell drops to a lower value as compared to the reported rank of
the Pcell in the first rank report.
14. The apparatus of claim 11, wherein the means for dynamically
configuring comprises: means for scheduling at least one of
activation or deactivation of the Scell at a transmission time
interval (TTI) level.
15. The apparatus of claim 11, wherein the means for receiving the
signal quality measurements comprises: means for receiving a first
rank report from the UE for the Pcell when the Scell is configured,
wherein the first rank report includes a reported rank of the
Pcell, and means for receiving a second rank report from the UE for
the Scell, wherein the second rank report includes a reported rank
of the Scell, wherein the means for dynamically configuring
comprises means for deactivating CA and means for handing over the
UE to the Scell for MIMO operation on the Scell, when the reported
rank for the Scell equals the number of antennas at the UE.
16. The apparatus of claim 15, further comprising: means for
configuring the UE for a lower-order MIMO operation and means for
activating CA when a subsequently reported rank of the Scell drops
to a lower value as compared to the reported rank of the Scell in
the second rank report.
17. An apparatus for determining a rank for a primary cell (Pcell)
and a secondary cell (Scell) in a wireless communication network,
the apparatus comprising: means for sampling, in a first time
interval, a reference signal in the Pcell using a first antenna set
and sampling a reference signal in the Scell using a second antenna
set; means for repeating the sampling step in a second time
interval; means for combining the sampled reference signals from
the first and second time intervals to determine a rank for the
Pcell and the Scell, respectively; and means for reporting the
determined rank of the Pcell and the Scell to the network.
18. The apparatus of claim 17, wherein the apparatus is a user
equipment (UE) in a carrier aggregation (CA) mode.
19. The apparatus of claim 17, wherein the apparatus is a user
equipment (UE) that does not have measurement gaps scheduled by the
network.
20. The apparatus of claim 17, wherein the means for repeating the
sampling step in the second time interval comprises: means for
sampling the reference signal in the Pcell using the second antenna
set and sampling the reference signal in the Scell using the first
antenna set.
Description
BACKGROUND
Field of Disclosure
Certain aspects of the claimed invention generally relate to
dynamically configuring one or more cells based on signal quality
measurements received from all antennas of a receiver-limited UE
capable of operating in a CA mode.
Description of Related Art
Wireless communication networks are widely deployed to provide
various communication services such as telephony, video, data,
messaging, broadcasts, and so on. Such networks, which are usually
multiple access networks, support communications for multiple users
by sharing the available network resources. For example, one
network may be a 3G (the third generation of mobile phone standards
and technology) system, which may provide network service via any
one of various 3G radio access technologies (RATs) including EVDO
(Evolution-Data Optimized), 1.times.RTT (1 times Radio Transmission
Technology, or simply 1.times.), W-CDMA (Wideband Code Division
Multiple Access), UMTS-TDD (Universal Mobile Telecommunications
System-Time Division Duplexing), HSPA (High Speed Packet Access),
GPRS (General Packet Radio Service), or EDGE (Enhanced Data rates
for Global Evolution). The 3G network is a wide area cellular
telephone network that evolved to incorporate high-speed internet
access and video telephony, in addition to voice calls.
Furthermore, a 3G network may be more established and provide
larger coverage areas than other network systems. Such multiple
access networks may also include code division multiple access
(CDMA) systems, time division multiple access (TDMA) systems,
frequency division multiple access (FDMA) systems, orthogonal
frequency division multiple access (OFDMA) systems, single-carrier
FDMA (SC-FDMA) networks, 3rd Generation Partnership Project (3GPP)
Long Term Evolution (LTE) networks, and Long Term Evolution
Advanced (LTE-A) networks.
A wireless communication network may include a number of base
stations that can support communication for a number of mobile
stations. A mobile station (MS) may communicate with a base station
(BS) via a downlink and an uplink. The downlink (or forward link)
refers to the communication link from the base station to the
mobile station, and the uplink (or reverse link) refers to the
communication link from the mobile station to the base station. A
base station may transmit data and control information on the
downlink to a mobile station and/or may receive data and control
information on the uplink from the mobile station.
A mobile station may have several receivers and antennas, which may
be shared by different applications and/or frequency bands. A
receiver-limited mobile station may refer to a mobile station in
which a number of receivers is less than or equal to a number of
antennas (N). Receiver-limited mobile stations may operate in
M.times.N multiple-input multiple-output (MIMO) in a non-carrier
aggregation (CA) mode, where M represents the number of antennas at
a transmitting device. However, because the mobile station is
"receiver-limited," it may only support M.times.(N/2) MIMO in
CA.
In a receiver-limited UE, once CA is configured and activated,
there may be no mechanism to check if the rank has improved on a
primary cell (Pcell) because the receivers are assigned to a
secondary cell (Scell), or vice versa. Under such circumstances,
the network may not be utilizing the spatial multiplexing gain
available and may be unnecessarily tying-up resources on the
Scell.
Since M.times.N MIMO on either the Pcell or Scell may be preferred,
what is needed are techniques and apparatus to detect a
receiver-limited UE and activate and/or deactivate one or more
cells accordingly.
SUMMARY
Certain aspects generally relate to a method for wireless
communication. The method generally includes receiving signal
quality measurements from all antennas of a receiver-limited UE
capable of operating in a CA mode, wherein a number of receivers of
the receiver-limited UE is less than or equal to a number of
antennas of the UE and dynamically configuring at least one of a
primary cell (Pcell) or a secondary cell (Scell) of the UE, based
at least in part, on the received signal quality measurements.
Certain aspects generally relate to an apparatus for wireless
communication. The apparatus generally includes means for receiving
signal quality measurements from all antennas of a receiver-limited
UE capable of operating in a CA mode, wherein a number of receivers
of the receiver-limited UE is less than or equal to a number of
antennas of the UE and means for dynamically configuring at least
one of a Pcell or a Scell of the UE, based at least in part, on the
received signal quality measurements.
Certain aspects generally relate to an apparatus for wireless
communication. The apparatus generally includes at least one
processor, a receiver, and a memory coupled to the at least one
processor with instructions stored thereon. The receiver is
generally configured to receive signal quality measurements from
all antennas of a receiver-limited UE capable of operating in a CA
mode, wherein a number of receivers of the receiver-limited UE is
less than or equal to a number of antennas of the UE. The at least
one processor is generally configured to dynamically configure at
least one of a Pcell or a Scell of the UE, based at least in part,
on the received signal quality measurements.
Certain aspects generally relate to a computer readable medium for
wireless communications having instructions stored thereon, the
instructions executable by one or more processors, for receiving
signal quality measurements from all antennas of a receiver-limited
UE capable of operating in a CA mode, wherein a number of receivers
of the receiver-limited UE is less than or equal to a number of
antennas of the UE and dynamically configuring at least one of a
Pcell or a Scell of the UE, based at least in part, on the received
signal quality measurements.
Certain aspects generally relate to a method for determining a rank
for a Pcell and a Scell in a wireless communication network. The
method generally includes sampling, in a first time interval, a
reference signal in the Pcell using a first antenna set and
sampling a reference signal in the Scell using a second antenna
set, repeating the sampling step in a second time interval,
combining the sampled reference signals from the first and second
time intervals to determine a rank for the Pcell and the Scell,
respectively, and reporting the determined rank of the Pcell and
the Scell to the network.
Certain aspects generally relate to an apparatus for determining a
rank for a Pcell and a Scell in a wireless communication network.
The apparatus generally includes means for sampling, in a first
time interval, a reference signal in the Pcell using a first
antenna set and sampling a reference signal in the Scell using a
second antenna set, means for repeating the sampling step in a
second time interval, means for combining the sampled reference
signals from the first and second time intervals to determine a
rank for the Pcell and the Scell, respectively, and means for
reporting the determined rank of the Pcell and the Scell to the
network.
Certain aspects generally relate to an apparatus for determining a
rank for a Pcell and a Scell in a wireless communication network.
The apparatus generally includes at least one processor, and
transmitter, and a memory having instructions stored thereon
coupled to the at least one processor. The at least one processor
is generally configured to sample, in a first time interval, a
reference signal in the Pcell using a first antenna set and
sampling a reference signal in the Scell using a second antenna
set, repeat the sampling step in a second time interval, and
combine the sampled reference signals from the first and second
time intervals to determine a rank for the Pcell and the Scell,
respectively. The transmitter is generally configured to report the
determined rank of the Pcell and the Scell to the network.
Certain aspects generally relate to a computer readable medium for
wireless communications having instructions stored thereon, the
instructions executable by one or more processors, for sampling, in
a first time interval, a reference signal in the Pcell using a
first antenna set and sampling a reference signal in the Scell
using a second antenna set, repeating the sampling step in a second
time interval, combining the sampled reference signals from the
first and second time intervals to determine a rank for the Pcell
and the Scell, respectively and reporting the determined rank of
the Pcell and the Scell to the network.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above-recited features of the
claimed invention can be understood in detail, a more particular
description, briefly summarized above, may be had by reference to
aspects, some of which are illustrated in the appended drawings. It
is to be noted, however, that the appended drawings illustrate only
certain typical aspects of the claimed invention and are therefore
not to be considered limiting of its scope, for the description may
admit to other equally effective aspects.
FIG. 1 illustrates an example wireless communications network in
accordance with various embodiments of the present invention.
FIG. 2 is a block diagram of an example AP and user terminals in
accordance with various embodiments of the present invention.
FIG. 3 is a block diagram of an example transceiver front end in
accordance with various embodiments of the present invention.
FIG. 4 illustrates an example of a non-receiver-limited UE,
according to various embodiments of the present invention.
FIG. 5 illustrates an example of a receiver-limited UE, according
to various embodiments of the present invention.
FIG. 6 illustrates an example architecture of a UE which utilizes a
switch such that all antennas may be used to measure a Pcell and
Scell without the use of assigned measurement gaps, according to
aspects various embodiments of the present invention.
FIG. 7 illustrates operations performed, for example, by network,
according to various embodiments of the present invention.
FIG. 8 illustrates operations performed, for example, by a UE,
according to various embodiments of the present invention.
DETAILED DESCRIPTION
Aspects of the claimed invention relate to a network (e.g., an
AP/eNB) dynamically configuring one or more cells (e.g., Pcell
and/or Scell) via the AP/eNB based on information received from a
receiver-limited UE, in an effort to allocate a highest rank for
each cell. Thus, aspects of the present invention provide
mechanisms to check, when CA is activated, if rank for a Pcell or
Scell has improved such that the UE may switch from CA mode to
multiple-input multiple-output (MIMO), thereby freeing up network
resources.
Further, aspects of the claimed invention as described herein,
provide methods and apparatus for a UE to construct a complete
channel matrix for both a Pcell and Scell. For example, absent
network-scheduled measurement gaps, UEs may use antenna swapping to
measure reference signals from both the Pcell and Scell, in an
effort to construct a complete (e.g., 4.times.4) channel matrix for
both the Pcell and the Scell. Further, while aspects of the claimed
invention may specifically relate to a 4.times.4 channel matrix,
one of ordinary skill in the art would understand that the claimed
invention may be implemented for any M.times.N channel matrix.
Various aspects of the claimed invention are described below. It
should be apparent that the teachings herein may be embodied in a
wide variety of forms and that any specific structure, function, or
both being disclosed herein is merely representative. Based on the
teachings herein, one skilled in the art should appreciate that an
aspect disclosed herein may be implemented independently of any
other aspects and that two or more of these aspects may be combined
in various ways. For example, an apparatus may be implemented or a
method may be practiced using any number of the aspects set forth
herein. In addition, such an apparatus may be implemented or such a
method may be practiced using other structure, functionality, or
structure and functionality in addition to or other than one or
more of the aspects set forth herein. Furthermore, an aspect may
comprise at least one element of a claim.
The word "exemplary" is used herein to mean "serving as an example,
instance, or illustration." Any aspect described herein as
"exemplary" is not necessarily to be construed as preferred or
advantageous over other aspects.
The techniques described herein may be used in combination with
various wireless technologies such as Code Division Multiple Access
(CDMA), Orthogonal Frequency Division Multiplexing (OFDM), Time
Division Multiple Access (TDMA), Spatial Division Multiple Access
(SDMA), Single Carrier Frequency Division Multiple Access
(SC-FDMA), Time Division Synchronous Code Division Multiple Access
(TD-SCDMA), and the like. Multiple user terminals can concurrently
transmit/receive data via different (1) orthogonal code channels
for CDMA, (2) time slots for TDMA, or (3) sub-bands for OFDM. A
CDMA system may implement IS-2000, IS-95, IS-856, Wideband-CDMA
(W-CDMA), or some other standards. An OFDM system may implement
Institute of Electrical and Electronics Engineers (IEEE) 802.11
(Wireless Local Area Network (WLAN)), IEEE 802.16 (Worldwide
Interoperability for Microwave Access (WiMAX)), Long Term Evolution
(LTE) (e.g., in TDD and/or FDD modes), or some other standards. A
TDMA system may implement Global System for Mobile Communications
(GSM) or some other standards. These various standards are known in
the art. The techniques described herein may also be implemented in
any of various other suitable wireless systems using radio
frequency (RF) technology, including Global Navigation Satellite
System (GNSS), Bluetooth, IEEE 802.15 (Wireless Personal Area
Network (WPAN)), Near Field Communication (NFC), Small Cell,
Frequency Modulation (FM), and the like.
An Example Wireless System
FIG. 1 illustrates an example wireless communication system in
which aspects of the claimed invention may be performed. For
example, a receiver-limited UE 120 may communicate with a network.
One or more APs 110 may define cellular regions (cells). The
network may receive signal quality measurements from all antennas
of the receiver-limited UE 120. The network may dynamically
configure one or more cells (not illustrated in FIG. 1) based, at
least in part, on the received signal quality measurements.
According to aspects, an AP (e.g., eNB) may configure one or more
cells including a Pcell and/or Scell based on the UE's CA
capabilities. Further, activation and deactivation of the Scell may
be performed by the AP using media access control (MAC)
signaling.
FIG. 1 illustrates a wireless communications system 100 with access
points and user terminals. For simplicity, only one access point
110 is shown in FIG. 1. An access point (AP) is generally a fixed
station that communicates with the user terminals and may also be
referred to as a base station (BS), an evolved Node B (eNB), or
some other terminology. A user terminal (UT) may be fixed or mobile
and may also be referred to as a mobile station (MS), an access
terminal, user equipment (UE), a station (STA), a client, a
wireless device, or some other terminology. A user terminal may be
a wireless device, such as a cellular phone, a personal digital
assistant (PDA), a handheld device, a wireless modem, a laptop
computer, a tablet, a personal computer, etc.
Access point 110 may communicate with one or more user terminals
120 at any given moment on the downlink and uplink. The downlink
(i.e., forward link) is the communication link from the access
point to the user terminals, and the uplink (i.e., reverse link) is
the communication link from the user terminals to the access point.
A user terminal may also communicate peer-to-peer with another user
terminal. A system controller 130 couples to and provides
coordination and control for the access points.
System 100 employs multiple transmit and multiple receive antennas
for data transmission on the downlink and uplink. Access point 110
may be equipped with a number N.sub.ap of antennas to achieve
transmit diversity for downlink transmissions and/or receive
diversity for uplink transmissions. A set N.sub.u of selected user
terminals 120 may receive downlink transmissions and transmit
uplink transmissions. Each selected user terminal transmits
user-specific data to and/or receives user-specific data from the
access point. In general, each selected user terminal may be
equipped with one or multiple antennas (i.e., N.sub.ut.gtoreq.1).
The N.sub.u selected user terminals can have the same or different
number of antennas.
Wireless system 100 may be a time division duplex (TDD) system or a
frequency division duplex (FDD) system. For a TDD system, the
downlink and uplink may share the same frequency band. For an FDD
system, the downlink and uplink use different frequency bands.
System 100 may also utilize a single carrier or multiple carriers
for transmission. Each user terminal may be equipped with a single
antenna (e.g., in order to keep costs down) or multiple antennas
(e.g., where the additional cost can be supported).
FIG. 2 illustrates an example access point and user terminal, which
may be used by to perform aspects of the claimed invention. For
example, a receiver-limited UE may include one or more modules
illustrated at UT 120. The network may receive signal quality
measurements from all antennas of the receiver-limited user
equipment UE, via an AP, and may dynamically configure one or more
cells based, at least in part, on the received signal quality
measurements. As shown in FIG. 1, the network may include one or
more access points, such as AP 110. Further, absent
network-scheduled measurement gaps, the UT 120, while operating in
a CA mode, may still construct a full channel matrix of both the
Pcell and Scell by swapping antennas as claimed and described
herein.
FIG. 2 shows a block diagram of access point 110 and two user
terminals 120m and 120x in wireless system 100. Access point 110 is
equipped with N.sub.ap antennas 224a through 224ap. User terminal
120m is equipped with N.sub.ut,m antennas 252ma through 252mu, and
user terminal 120x is equipped with N.sub.ut,x antennas 252xa
through 252xu. Access point 110 is a transmitting entity for the
downlink and a receiving entity for the uplink. Each user terminal
120 is a transmitting entity for the uplink and a receiving entity
for the downlink. As used herein, a "transmitting entity" is an
independently operated apparatus or device capable of transmitting
data via a frequency channel, and a "receiving entity" is an
independently operated apparatus or device capable of receiving
data via a frequency channel. In the following description, the
subscript "dn" denotes the downlink, the subscript "up" denotes the
uplink, N.sub.up user terminals are selected for simultaneous
transmission on the uplink, N.sub.dn user terminals are selected
for simultaneous transmission on the downlink, N.sub.up may or may
not be equal to N.sub.dn, and N.sub.up and N.sub.dn may be static
values or can change for each scheduling interval. Beam-steering or
some other spatial processing technique may be used at the access
point and user terminal.
On the uplink, at each user terminal 120 selected for uplink
transmission, a TX data processor 288 receives traffic data from a
data source 286 and control data from a controller 280. TX data
processor 288 processes (e.g., encodes, interleaves, and modulates)
the traffic data {d.sub.up} for the user terminal based on the
coding and modulation schemes associated with the rate selected for
the user terminal and provides a data symbol stream {s.sub.up} for
one of the N.sub.ut,m antennas. A transceiver front end (TX/RX) 254
(also known as a radio frequency front end (RFFE)) receives and
processes (e.g., converts to analog, amplifies, filters, and
frequency upconverts) a respective symbol stream to generate an
uplink signal. The transceiver front end 254 may also route the
uplink signal to one of the N.sub.ut,m antennas for transmit
diversity via an RF switch, for example. The controller 280 may
control the routing within the transceiver front end 254.
A number N.sub.up of user terminals may be scheduled for
simultaneous transmission on the uplink. Each of these user
terminals transmits its set of processed symbol streams on the
uplink to the access point.
At access point 110, N.sub.ap antennas 224a through 224ap receive
the uplink signals from all N.sub.up user terminals transmitting on
the uplink. For receive diversity, a transceiver front end 222 may
select signals received from one of the antennas 224 for
processing. For certain aspects of the present disclosure, a
combination of the signals received from multiple antennas 224 may
be combined for enhanced receive diversity. The access point's
transceiver front end 222 also performs processing complementary to
that performed by the user terminal's transceiver front end 254 and
provides a recovered uplink data symbol stream. The recovered
uplink data symbol stream is an estimate of a data symbol stream
{s.sub.up} transmitted by a user terminal. An RX data processor 242
processes (e.g., demodulates, deinterleaves, and decodes) the
recovered uplink data symbol stream in accordance with the rate
used for that stream to obtain decoded data. The decoded data for
each user terminal may be provided to a data sink 244 for storage
and/or a controller 230 for further processing.
On the downlink, at access point 110, a TX data processor 210
receives traffic data from a data source 208 for N.sub.dn user
terminals scheduled for downlink transmission, control data from a
controller 230 and possibly other data from a scheduler 234. The
various types of data may be sent on different transport channels.
TX data processor 210 processes (e.g., encodes, interleaves, and
modulates) the traffic data for each user terminal based on the
rate selected for that user terminal TX data processor 210 may
provide a downlink data symbol streams for one of more of the
N.sub.dn user terminals to be transmitted from one of the N.sub.ap
antennas. The transceiver front end 222 receives and processes
(e.g., converts to analog, amplifies, filters, and frequency
upconverts) the symbol stream to generate a downlink signal. The
transceiver front end 222 may also route the downlink signal to one
or more of the N.sub.ap antennas 224 for transmit diversity via an
RF switch, for example. The controller 230 may control the routing
within the transceiver front end 222.
At each user terminal 120, N.sub.ut,m antennas 252 receive the
downlink signals from access point 110. For receive diversity at
the user terminal 120, the transceiver front end 254 may select
signals received from one of the antennas 252 for processing. For
certain aspects of the present disclosure, a combination of the
signals received from multiple antennas 252 may be combined for
enhanced receive diversity. The user terminal's transceiver front
end 254 also performs processing complementary to that performed by
the access point's transceiver front end 222 and provides a
recovered downlink data symbol stream. An RX data processor 270
processes (e.g., demodulates, deinterleaves, and decodes) the
recovered downlink data symbol stream to obtain decoded data for
the user terminal.
Those skilled in the art will recognize the techniques described
herein may be generally applied in systems utilizing any type of
multiple access schemes, such as TDMA, SDMA, Orthogonal Frequency
Division Multiple Access (OFDMA), CDMA, SC-FDMA, and combinations
thereof.
FIG. 3 illustrates example transceiver front end that may be used
to implement aspects of the claimed invention.
FIG. 3 is a block diagram of an example transceiver front end 300,
such as transceiver front ends 222, 254 in FIG. 2, in accordance
with certain aspects of the present disclosure. The transceiver
front end 300 includes a transmit (TX) path 302 (also known as a
transmit chain) for transmitting signals via one or more antennas
and a receive (RX) path 304 (also known as a receive chain) for
receiving signals via the antennas. When the TX path 302 and the RX
path 304 share an antenna 303, the paths may be connected with the
antenna via an interface 306, which may include any of various
suitable RF devices, such as a duplexer, a switch, a diplexer, and
the like.
Receiving in-phase (I) or quadrature (Q) baseband analog signals
from a digital-to-analog converter (DAC) 308, the TX path 302 may
include a baseband filter (BBF) 310, a mixer 312, a driver
amplifier (DA) 314, and a power amplifier 316. The BBF 310, the
mixer 312, and the DA 314 may be included in a radio frequency
integrated circuit (RFIC), while the PA 316 is often external to
the RFIC. The BBF 310 filters the baseband signals received from
the DAC 308, and the mixer 312 mixes the filtered baseband signals
with a transmit local oscillator (LO) signal to convert the
baseband signal of interest to a different frequency (e.g.,
upconvert from baseband to RF). This frequency conversion process
produces the sum and difference frequencies of the LO frequency and
the frequency of the signal of interest. The sum and difference
frequencies are referred to as the beat frequencies. The beat
frequencies are typically in the RF range, such that the signals
output by the mixer 312 are typically RF signals, which are
amplified by the DA 314 and by the PA 316 before transmission by
the antenna 303.
The RX path 304 includes a low noise amplifier (LNA) 322, a mixer
324, and a baseband filter (BBF) 326. The LNA 322, the mixer 324,
and the BBF 326 may be included in a radio frequency integrated
circuit (RFIC), which may or may not be the same RFIC that includes
the TX path components. RF signals received via the antenna 303 may
be amplified by the LNA 322, and the mixer 324 mixes the amplified
RF signals with a receive local oscillator (LO) signal to convert
the RF signal of interest to a different baseband frequency (i.e.,
downconvert). The baseband signals output by the mixer 324 may be
filtered by the BBF 326 before being converted by an
analog-to-digital converter (ADC) 328 to digital I or Q signals for
digital signal processing.
While it is desirable for the output of a LO to remain stable in
frequency, tuning to different frequencies indicates using a
variable-frequency oscillator, which involves compromises between
stability and tunability. Contemporary systems employ frequency
synthesizers with a voltage-controlled oscillator (VCO) to generate
a stable, tunable LO with a particular tuning range. Thus, the
transmit LO is typically produced by a TX frequency synthesizer
318, which may be buffered or amplified by amplifier 320 before
being mixed with the baseband signals in the mixer 312. Similarly,
the receive LO is typically produced by an RX frequency synthesizer
330, which may be buffered or amplified by amplifier 332 before
being mixed with the RF signals in the mixer 324.
Example Mechanism to Allocate a Highest Possible Rank for Each Cell
in a CA Mode Receiver-Limited UE
Cellular devices that have a same number of antennas (N) as
receivers and which support carrier aggregation (CA) may operate in
M.times.N MIMO in non-CA mode, where M is a number of antennas at
the transmitter and may only support M.times.(N/2) MIMO in CA,
because the UE is "receiver-limited." In a receiver-limited UE,
once CA is configured and activated, there may be no mechanism to
check if the rank has improved on the primary cell (Pcell) because,
for example, the receivers are assigned to a secondary cell (Scell)
(or vice versa). Under such circumstances, the network may not be
utilizing the spatial multiplexing gain available and may be
unnecessarily tying-up resources, for example, on the Scell.
As described above, cellular devices (e.g., UEs) may have several
receivers and antennas. The multiple receivers may be shared
between different applications and/or frequency bands, such that
certain UEs have more antennas available for cellular purposes than
RF receivers. As described above, a problem may arise where a UE
allocates its receivers to a Scell and is unable to maximize the
spatial multiplexing gain the UE is capable of.
FIG. 4 illustrates an example design architecture 400 of a
non-receiver-limited UE. The design architecture 400 may support
2.times.2 MIMO in CA as well as non-CA mode. As illustrated, the
duplexers allow inter-band Pcells and Scells to share antennas. For
the non-receiver limited UE shown in FIG. 4, the number of
receivers (4 receivers illustrated) equals 2*the number of antennas
(2 antennas illustrated), as illustrated in FIG. 4.
FIG. 5 illustrates an example design architecture 500 of a
receiver-limited UE, according to aspects of the claimed invention.
The design architecture 500 may support 4.times.4 MIMO in non-CA
mode but may only support 2.times.2 MIMO in CA mode. In other
words, even with duplexers the UE may not support 4.times.4 MIMO
and CA mode due to its RF receiver limitation. The UE of FIG. 5 is
receiver-limited as the number of receivers (4 receivers
illustrated) is less than or equal to the number of antennas (4
antennas illustrated).
A UE having the design architecture illustrated in and described
with reference to FIG. 5 may need to optionally switch between
4.times.4 MIMO and CA. In CA scenarios, if a Category 5 (CATS) or
higher UE reports a rank 4 on the Pcell, the network may free-up
Scell resources by switching from the CA mode to 4.times.4 MIMO on
the Pcell. The switch from CA to MIMO may occur at a transmission
time interval (TTI) every 1 ms.
When CA is activated, however, the receivers of the UE are split
between the Pcell and Scell. Accordingly, there is no mechanism to
check if the rank has improved for either the Pcell or Scell in an
effort to determine to switch from CA to MIMO.
As described above, a receiver-limited UE, as illustrated in FIG.
5, may have a number of antennas (N) that is greater than or equal
to the number of as receivers. Accordingly, the receiver-limited UE
and may support CA in M.times.N MIMO in non-CA mode, but may only
support M.times.(N/2) MIMO in CA mode. As M.times.N MIMO may be
preferred over M.times.(N/2) MIMO, aspects of the claimed invention
provide mechanisms where the network may detect a receiver-limited
UE and configure and/or activate the one or more cells or MIMO
based on this knowledge. Accordingly, the network may configure
measurement gaps for rank determination by a UE, as necessary.
According to aspects of the claimed invention, and as will be
described in more detail herein, the UE may perform periodic
antenna switching to measure the rank on the Pcell and Scell when
gaps are not available (e.g., when measurements gaps are not
scheduled by the network) in an effort to construct a full channel
matrix for both the Pcell and the Scell.
According to aspects, a UE with four antennas may be operating in a
CA mode. The Scell may be configured and activated. The UE may
measure signal quality on all 4 antennas and may report the rank to
the network (e.g., on the Pcell) in a first rank report. If the
reported rank is 4, the network may choose to deactivate the Scell
and assign 4.times.4 MIMO to the UE on the Pcell. If the reported
rank changes to a lower value at any time after the first rank
report, the network may choose to move to a lower order MIMO, and
activate the Scell for CA. As described above, the switch between
modes (CA and MIMO) may be performed at a TTI level. According to
aspects, Scell activation/deactivation may be performed at the MAC
level at a TTI level.
According to aspects, the UE may measure signal quality on both the
Pcell and Scell and report the rank of both cells to the network.
For example, a first rank report may include a reported rank of the
Pcell and a second rank report may include a reported rank of the
Scell. If the reported rank is 4 on the Scell, the network may
choose to handover to the Scell, deactivate CA, and assign
4.times.4 MIMO on the Scell. If the reported rank of the Scell
changes to a lower value at any time after the second rank report,
the network may choose to move to a lower order MIMO and activate
CA.
A UE supporting 4.times.4 MIMO may achieve similar throughput as
the UE supporting 2.times.2 MIMO in CA mode. For example, the peak
throughput for a 10 MHz cell with 4.times.4 MIMO support (4 layers)
is 150 Mbps. The peak throughout in CA mode for a 10 MHz Pcell and
10 MHz Scell with 2.times.2 MIMO is around 150 Mbps. Therefore,
aspects of the claimed invention may advantageously free up
resources on the Scell, thereby increasing the capacity of the
system, while maintaining similar throughput. Further, changing
(e.g., switching) from 4.times.4 MIMO to 2.times.2 MIMO in CA mode
may be performed at the MAC level, thereby allowing fast channel
adaptation.
According to aspects of the claimed invention, the network may
detect a receiver-limited UE by taking into account the UE category
and CA MIMO capability. For example, when a Category 5 or higher UE
reports only M.times.2 MIMO capability for CA band combinations,
where M is the number of antennas at the transmitter, the UE is
considered to be receiver-limited for this band combination. The
network may configure and/or activate the Scell based on the CA
scenario and Scell state as described below.
According to a first scenario, the CA capable UE may be operating
in a non-CA mode. An eNB communicating with the UE may have a
4.times.4 antenna configuration. If the UE reports Rank 4 (e.g.,
rank indicator (RI)=4) on the Pcell, the network may not configure
and activate the Scell. Instead, the network may configure and
activate the Scell when the UE reports Rank 2 for the Pcell to the
network, as 4.times.4 MIMO for the Pcell may not be possible at
that time.
According to a second scenario, the Scell may be configured but not
activated. In this case, the UE may be able to measure the rank
supported by periodically using Scell antenna ports and tuning away
receivers for calculating a M.times.N (e.g., 4.times.4) channel
matrix for the Pcell. Once the UE reports Rank 4, the network has
the option of removing the Scell configuration and providing
4.times.4 grants to the UE. The network may not activate the Scell
as long as the UE is reporting Rank 4 capabilities for the Pcell.
For Scell periodic measurements, the network may configure
measurement gaps. Additionally or alternatively, the network may
provide 2.times.2 grants so that the UE can measure the Scell on
the available RF chains. This may also be achieved by the UE
periodically dropping the rank capability to 2.
According to a third scenario, the Scell may be configured and
activated. In this case, the UE may use measurements gaps to
measure M.times.4 channel matrix (e.g., Rank 4) supported for both
the Pcell and Scell. If the Pcell and/or Scell are strong and gaps
are not scheduled for inter-frequency/inter-band/RAT neighbors, the
network may initiate gaps for measuring the highest possible rank
for receiver-limited UEs. According to aspects when gaps are not
able to be scheduled (e.g., during a CA active state), the UE may
use antenna switching, as will be described in more detail with
reference to FIG. 6, in an effort to determine the channel state on
all antennas. The UE my combine the channel state received from all
antennas in an effort to determine the highest rank for both the
Pcell and Scell. Once the UE reports a Rank 4, for example, for the
Pcell, the network may deactivate and/or remove the Scell
configuration.
FIG. 6 illustrates an example of swapping 600 antennas at a UE in
an effort to determine a rank for the Pcell and Scell, according to
aspects of the claimed invention. During a CA activated state,
measurement gaps may not be available, since the Scell is
continuously active. According to aspects of the claimed invention,
the UE may still determine a rank of the Pcell and Scell when the
network has not scheduled measurement gaps.
In a CA active state, the UE may use two antennas for measuring a
reference signal in the Pcell and two antennas for measuring a
reference signal in the Scell. Antenna switching (e.g., swapping)
may be used to sample the Pcell reference signal from Scell
antennas and sample the Scell reference signal from Pcell antennas,
thereby constructing a complete 4.times.4 channel matrix for both
the Pcell and Scell.
For example, during a first time interval (e.g., t1), Antennas 0
and 1 may be used to sample a first and second (Rx0 and Rx1,
respectively) channel of the Pcell. During a different time
interval (e.g., a second time interval, t2), Antennas 2 and 3 may
be used to sample a third and fourth (Rx2 and Rx3, respectively)
channel of the Pcell. The UE may combine the measurements from
Antennas 0-4 to determine a rank for the Pcell.
Similarly, during a time interval, for example, during the first
time interval t1, while Antennas 0 and 1 may be used to sample a
first and second (Rx0 and Rx1, respectively) channel of the Pcell,
Antennas 2 and 3 may be used to sample a first and second (Rx0 and
Rx1, respectively) channel of the Scell. During the different time
interval (e.g., second time interval, t2), Antennas 0 and 1 may be
used to measure the Scell (e.g., Rx2 and Rx3 of the Scell). The UE
may combine the measurements from Antennas 0-4 to determine a rank
for the Scell.
In this manner, when both the Pcell and Scell are CA activated, the
UE may determine a rank of the Pcell and Scell without
network-scheduled measurement gaps. As described above, the UE may
swap antennas to determine a rank for both the Pcell and Scell,
thereby constructing a complete 4.times.4 channel matrix for both
the Pcell and Scell. While a 4.times.4 channel matrix is used as an
example for a full channel matrix, one of ordinary skill in the art
would understand that aspects of the claimed invention may be
implemented for any M.times.N channel matrix.
FIG. 7 illustrates example operations, performed for example, by a
network (e.g., an AP, such as APs 110 of FIGS. 1 and 2) in
communication with a receiver-limited UE, according to aspects of
the claimed invention. One or more modules of AP 110 of FIG. 2 may
perform the operations. For example, Tx/Rx 222, antennas 224,
controller 230, memory 232, and processors 210 and 242 may perform
the operations described herein.
At 702, the network may receive signal quality measurements from
all antennas of a receiver-limited UE capable of operating in a CA
mode. A UE may be receiver-limited when the number receivers at the
UE is less than or equal to a number of antennas at the UE.
At 704, the network may dynamically configure one or more cells
(e.g., Pcell and/or Scell) based, at least in part, on the received
signal quality measurements.
According to aspects of the claimed invention, receiving the signal
quality measurement includes receiving a first rank report from the
UE for a Pcell when a Scell is configured. The first rank report
may include a reported rank of the Pcell. When the reported rank of
the Pcell equals the number of antennas at the UE, the network may
deactivate the Scell and configure the UE for MIMO operation on the
Pcell.
According to aspects of the claimed invention, the network may
further configure the UE for a lower-order MIMO operation and
activate the Scell when a subsequently reported rank of the Pcell
changes to a lower value as compared to the reported rank of the
Pcell in the first rank report.
According to aspects of the claimed invention, the network may
dynamically configure the one or more cells by scheduling at least
one of activation or deactivation of a Scell at a TTI level.
In addition to receiving the first rank report, which includes a
reported rank of the Pcell from the UE for the Pcell, the network
may receive a second rank report when the Scell is configured. The
second rank report may include a report rank of the Scell. When the
reported rank for the Scell equals a number of antennas at the UE,
the network may deactivate CA and handover the UE to the Scell for
MIMO operation on the Scell.
Further, the network may configure the UE for a lower-order MIMO
operation and activate CA when a subsequently reported rank of the
Scell drops to a lower value as compared to the reported rank of
the Scell in the second rank report.
As described above, the network (e.g., an AP) may detect a
receiver-limited UE based, at least in part, on a UE category and
reported MIMO capability. For example, the network may detected a
UE as being receiver-limited when it is a Category 5 or higher UE
and reports a maximum of 2.times.2 MIMO support for each CA band
combination.
FIG. 8 illustrates operations 800, performed, for example by a UE
for determining a rank for a Pcell and a Scell. The operations may
be performed by one or more modules of UT 120 in FIG. 2. For
example, antenna 252, Tx/Rx 254, controller 280, memory 282, and
processors 270 and 288 may perform the operations described
herein.
At 802, the UE may sample, in a first time interval, a reference
signal in the Pcell using a first antenna set and sampling a
reference signal in the Scell using a second antenna set. At 804,
the UE may repeat the sampling step in a second time interval. As
described with reference to FIG. 6, the UE may repeat the sampling
step in the second time interval by sampling the reference signal
in the Pcell using the second antenna set and sampling the
reference signal in the Scell using the first antenna set.
At 806, the UE may combine the sampled reference signals from the
first and second time intervals to determine a rank for the Pcell
and the Scell, respectively. At 808, the UE may report the
determined rank of the Pcell and the Scell to the network.
As described above, the UE performing the operations illustrated in
FIG. 8 may be a UE operating in a CA mode. The UE may not have
network-scheduled measurement gaps. Absent network-scheduled
measurement gaps, the UE may be able to construct a full channel
matrix for the Pcell and the Scell using aspects of the claimed
invention.
In this manner, the UE may determine a rank of the Pcell and the
Scell by swapping (e.g., switching) antennas. In other words, an
antenna switch may be used such that Pcell and Scell reference
signals may be measured from all antennas at a UE even when the UE
does not have scheduled measurement gaps in which to measure
reference signals on the Pcell or Scell.
As used herein, the term "determining" encompasses a wide variety
of actions. For example, "determining" may include calculating,
computing, processing, deriving, investigating, looking up (e.g.,
looking up in a table, a database or another data structure),
ascertaining and the like. Also, "determining" may include
receiving (e.g., receiving information), accessing (e.g., accessing
data in a memory) and the like. Also, "determining" may include
resolving, selecting, choosing, establishing and the like.
As used herein, a phrase referring to "at least one of" a list of
items refers to any combination of those items, including single
members. As an example, "at least one of: a, b, or c" is intended
to cover: a, b, c, a-b, a-c, b-c, and a-b-c.
The various illustrative logical blocks, modules and circuits
described in connection with the claimed invention may be
implemented or performed with a general purpose processor, a
digital signal processor (DSP), an application specific integrated
circuit (ASIC), a field programmable gate array (FPGA) or other
programmable logic device (PLD), discrete gate or transistor logic,
discrete hardware components, or any combination thereof designed
to perform the functions described herein. A general-purpose
processor may be a microprocessor, but in the alternative, the
processor may be any commercially available processor, controller,
microcontroller, or state machine. A processor may also be
implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
The methods disclosed herein comprise one or more steps or actions
for achieving the described method. The method steps and/or actions
may be interchanged with one another without departing from the
scope of the claims. In other words, unless a specific order of
steps or actions is specified, the order and/or use of specific
steps and/or actions may be modified without departing from the
scope of the claims.
The functions described may be implemented in hardware, software,
firmware, or any combination thereof. If implemented in hardware,
an example hardware configuration may comprise a processing system
in a wireless node. The processing system may be implemented with a
bus architecture. The bus may include any number of interconnecting
buses and bridges depending on the specific application of the
processing system and the overall design constraints. The bus may
link together various circuits including a processor,
machine-readable media, and a bus interface. The bus interface may
be used to connect a network adapter, among other things, to the
processing system via the bus. The network adapter may be used to
implement the signal processing functions of the PHY layer. In the
case of a user terminal 120 (see FIG. 1), a user interface (e.g.,
keypad, display, mouse, joystick, etc.) may also be connected to
the bus. The bus may also link various other circuits such as
timing sources, peripherals, voltage regulators, power management
circuits, and the like, which are well known in the art, and
therefore, will not be described any further.
The processing system may be configured as a general-purpose
processing system with one or more microprocessors providing the
processor functionality and external memory providing at least a
portion of the machine-readable media, all linked together with
other supporting circuitry through an external bus architecture.
Alternatively, the processing system may be implemented with an
ASIC (Application Specific Integrated Circuit) with the processor,
the bus interface, the user interface in the case of an access
terminal), supporting circuitry, and at least a portion of the
machine-readable media integrated into a single chip, or with one
or more FPGAs (Field Programmable Gate Arrays), PLDs (Programmable
Logic Devices), controllers, state machines, gated logic, discrete
hardware components, or any other suitable circuitry, or any
combination of circuits that can perform the various functionality
described throughout this disclosure. Those skilled in the art will
recognize how best to implement the described functionality for the
processing system depending on the particular application and the
overall design constraints imposed on the overall system.
It is to be understood that the claims are not limited to the
precise configuration and components illustrated above. Various
modifications, changes and variations may be made in the
arrangement, operation and details of the methods and apparatus
described above without departing from the scope of the claims.
* * * * *